and there is no op-tion to quit a running app in right-click dock menu. Dock icons for some of the running apps have lights, but quitting the app from the dock is initially unsuccessful. Icon either initially, or after quitting the app disiplays 'force qut', which, when clicked, doesn't work, either. Left-clicking the icon (thats the 3rd click) finaly kills the app and removes the icon from the dock.
Command + Q is the quickest way to quit a running Application. Click its icon in the Dock to give it focus, then press Command Q keys and its gone. No need to mess about with right clicking and selecting.